This application is a 35 USC371 of PCT/JP00/01492 filed Mar. 13, 2000.
The present invention relates to a method of continuously rolling a plurality of steel strips while controlling gaps therebetween.
There has been known a method of improving a rolling efficiency by reducing an interval between steel strips in such a manner that, between a preceding steel strip and a succeeding steel strip in a conventional one-way rolling and between the final path of a preceding steel strip and the first path of a succeeding steel strip in reverse rolling, a position of the trailing end of the preceding steel strip is determined from a rolling speed of the preceding steel strip, a predicted value of a backward ratio and a length of the steel strip as well as a position of the leading end of the succeeding steel strip is determined by a transportation speed of the succeeding steel strip calculated based on values detected by number of rotation detectors mounted on transportation tables and a moving distance of the succeeding steel strip from a leading end detector, an interval between the trailing end of the preceding steel strip which is being rolled and the leading end of the succeeding steel strip is determined from a difference between the thus determined positions is determined and used as a measured value, and speeds of the transportation tables at the inlet side and the outlet side of a rolling mill and a speed of the rolling mill are controlled based on the measured value.
However, when the above method is applied to a rolling method of simultaneously manufacturing a plurality of steel strips by disposing a plurality of the steel strips in a rolling direction and subjecting them to reverse rolling at the same time, measured intervals between the steel strips are greatly different from actual intervals therebetween due to a prediction error of a backward ratio and a variation of the backward ratio during rolling, an error of a rolling speed caused by thermal deformation and wear of rolls, and an error of a transportation speed of a succeeding steel strip and an error of a moving distance of the succeeding steel strip from the leading position detector which are caused by slip between steel strips being transported and the transportation tables. Therefore, there is arisen a drawback that inter-strip control of high accuracy cannot be carried out.
An object of the present invention, which was made to overcome the above drawback, is to provide a rolling method capable of dramatically improving a rolling efficiency by permitting a plurality of steel strips to be subjected not only to one-way rolling but also to reverse rolling at the same time by performing interstrip control of high accuracy.
To achieve the above object, a rolling method according to claim 1 is characterized in that interval measuring means for directly measuring an actual interval between the trailing end of a preceding steel strip and the leading end of a succeeding steel strip are disposed on the inlet side and the outlet side of a rolling mill, respectively and transportation speeds of the preceding steel strip and the succeeding steel strip are controlled separately from a speed of the rolling mill based on measured values obtained by the interval measuring means on the inlet side and the outlet side.
A rolling method according to claim 2 is characterized in claim 1 in that speeds of inlet side transportation tables for transporting the succeeding steel strip are controlled so that measured values, before the preceding steel strip is caught by the rolling mill, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the inlet side interval measuring device, are set to a first set value preset as an interval at which the preceding steel strip does not come into collision with the succeeding steel strip due to a reduction in speed which is caused when the preceding steel strip is caught by the rolling mill, speeds of the inlet side transportation tables for transporting the succeeding steel strip are controlled separately from a speed of the rolling mill so that measured values, when the preceding steel strip is being rolled, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the inlet side interval measuring device, are set to a second set value preset as an interval at which the succeeding steel strip is caught by the rolling mill at the same time at which the trailing end of the preceding steel strip has passed through the rolling mill, and speeds of outlet side transportation tables for transporting the preceding steel strip are controlled separately from a speed of the rolling mill so that measured values, when the succeeding steel strip is being rolled, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the outlet side interval measuring device, is set to a third set value preset as an optimum interval in rolling in a next process.
A rolling method according to claim 3 for disposing interval measuring means, which directly measures an actual interval between the trailing end of a preceding steel strip and the leading end of a succeeding steel strip, at an inlet side and an outlet side of a rolling mill, respectively and controlling transportation speeds of the preceding steel strip and the succeeding steel strip based on measured values which have been obtained by the interval measuring means at the inlet side and the outlet side is characterized in that speeds of inlet side transportation tables for transporting the succeeding steel strip are controlled so that measured values, before the preceding steel strip is caught by the rolling mill, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the inlet side interval measuring device, are set to a first preset value as an interval at which the preceding steel strip doe s not come into collision with the succeeding steel strip due to a reduction in speed which is caused when the preceding steel strip is caught by the rolling mill, speeds of the in let side transportation tables for transporting the succeeding steel strip are comprehensively controlled together with a speed of the rolling mill so that measured values, when the preceding steel strip is being rolled, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the inlet side interval measuring device, are set to a second set value preset as an interval at which the succeeding steel strip is caught by the rolling mill at the same time at which the trailing end of the preceding steel strip has passed through the rolling mill, and speeds of outlet side transportation tables for transporting the preceding steel strip are comprehensively controlled together with a speed of the rolling mill so that measured values, when the succeeding steel strip is being rolled, of an interval between the trailing end of the preceding steel strip and the leading end of the succeeding steel strip, which have been obtained by the outlet side interval measuring device, is set to a third set value preset as an optimum interval in rolling in a next process.